Influence of OH- and Nd3+ concentrations on the lifetimes of the Nd3+: F-4(3/2) level in PbO-Bi2O3-Ga2O3 glasses

Effects of the spurious OH- on the emission characteristics of Nd3+ doped P bO=Bi2O3-Ga2O3 glasses were investigated. Analyses on the decaying behaviou r of 1 . 35 mu m fluorescence from the F-4 (3/2) --> I-4 (13/2) transition in Nd3+ suggested the presence of two different energy transfer mechanisms between Nd3+ and OH-. For glasses with low concentration similar to 0 . 05 wt% Nd2O3, intensity of the emission showed a nonexponential decaying behav iour following the relationship of exp(t(0 . 5)) where t represents a time scale. In this case, a direct energy transfer from Nd3+ to OH- was responsi ble for the decay. The critical transfer distance (R-0) is approximately 0 . 46 nm. On the other hand, an exponential behaviour was dominant for glass es containing more than 0 . 5 wt% Nd2O3. Nonradiative decay in these glasse s is mainly originated from the migration assisted cross relaxation of F-4 (3/2):I-4 (9/2) --> I-4 (15/2):I-4 (15/2) type among the neighbouring Nd3instead of a direct energy transfer from Nd3+ to OH-.